Obviously if any actions, even a lunatic's, can be causeless, determinism is done for. If the chain of causation can be broken for a madman, it can be broken for a man.
But to see her was to love her, Love but her, and love forever. Had we never lou'd sae kindly, Had we never lou'd sae blindly, Never met - or never parted - We had ne'er been broken hearted